Keto, low-fat, paleo, intermittent fasting, carnivore — head-to-head trials repeatedly find that when calories and protein are matched, the differences between diets are small. What actually predicts weight loss is energy balance (eating less than you burn), and what predicts keeping it off is adherence — whether you can actually live this way. Every diet that works does so mostly by making you eat less, usually by eliminating a whole category of food you were overeating.
This is why the diet debate is largely misframed. The question isn't 'which diet is metabolically superior' but 'which set of rules can you follow for years without feeling deprived.' Someone who hates meat will fail on carnivore no matter what the metabolic literature says. The best diet is the one that fits your food preferences, culture, schedule, and budget — because a diet you quit has an effectiveness of zero.